4-(4-Aminophenylsulfonyl)anilinium toluene-4-sulfonate

In the title p-toluenesulfonate salt of the drug dapsone, C12H13N2O2S+·C7H7O3S−, the dihedral angle between the two aromatic rings of the dapsone monocation is 70.19 (17)° and those between these rings and that of the p-toluenesulfonate anion are 72.34 (17) and 46.43 (17)°. All amine and aminium H atoms are involved in intermolecular N—H⋯O hydrogen-bonding associations with sulfonyl O-atom acceptors as well as one of the sulfone O atoms, giving a three-dimensional structure.

In the title p-toluenesulfonate salt of the drug dapsone, C 12 H 13 N 2 O 2 S + ÁC 7 H 7 O 3 S À , the dihedral angle between the two aromatic rings of the dapsone monocation is 70.19 (17) and those between these rings and that of the p-toluenesulfonate anion are 72.34 (17) and 46.43 (17) . All amine and aminium H atoms are involved in intermolecular N-HÁ Á ÁO hydrogenbonding associations with sulfonyl O-atom acceptors as well as one of the sulfone O atoms, giving a three-dimensional structure.

Comment
Dapsone [4-(4-aminophenylsulfonyl)aniline] is a very weak Lewis base which finds use as an anti-leprotic, anti-malarial and leprostatic drug (Wilson et al., 1991). The structure of four dapsone solvates are known: the 0.33hydrate (Kus'mina et al., 1981)  In the crystal, all amine and aminium H-atoms are involved in intermolecular N-H···O hydrogen-bonding associations with sulfonyl O-atom acceptors as well as with one of the sulfone O-atoms (O11) ( Table 1). The resulting structure is a three-dimensional framework (Fig. 2). No π-π interactions are found between the cation and anion ring systems [minimum ring centroid separation = 4.534 (2) Å].

Experimental
The title compound was prepared by the reaction of 4-(4-aminophenylsulfonyl)aniline (dapsone) with p-toluenesulfonic acid by heating together for 15 min under reflux, 1 mmol quantities of the two reagents in 50 ml of 50% ethanol-water.
Partial room-temperature evaporation of the solvent provided poorly-formed colourless crystal aggregates of the title salt from which a specimen was cleaved for the X-ray analysis.

Refinement
All H atoms potentially involved in hydrogen-bonding associations were located in a difference-Fourier analysis but were subsequently constrained, with U iso (H) = 1.2U eq (N). Other H-atoms were included at calculated positions [C-H = 0.95 Å (aromatic) or 0.98 Å (methyl)] and also treated as riding, with U iso (H) = 1.2 or 1.5U eq (C).

Figure 1
The molecular conformation and atom-numbering scheme for the dapsone monocation and p-toluenesulfonate anion in the title salt. Non-H atoms are shown as 40% probability displacement ellipsoids and the inter-species hydrogen bond is shown as a dashed line.  The hydrogen-bonding in the title salt, viewed down the a axial direction of the unit cell. Hydrogen bonds are shown as dashed lines. For symmetry codes see Table 1.  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.33 e Å −3 Δρ min = −0.39 e Å −3 Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.